I. Field
The present invention relates generally to geolocation and location services for wireless devices. More particularly the invention relates to modifying geolocation data with local location data.
II. Background
This invention relates to locating and tracking mobile devices, such as wireless communication devices (WCDs).
The term WCD as used herein includes, but is not limited to, a user equipment, mobile station, fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment. WCDs include personal communication devices, such as phones, pagers, video phones, and Internet ready phones that have network connections. In addition, WCDs include portable personal computing devices, such as PDAs and notebook computers with wireless modems that have similar network capabilities. WCDs that are portable or can otherwise change location are referred to as mobile units. Wireless communication systems are widely deployed to provide various types of communication such as voice and data. A typical wireless data system, or network, provides multiple users access to one or more shared resources. A system may use a variety of multiple access techniques such as frequency division multiplexing (FDM), time division multiplexing (TDM), code division multiplexing (CDM), and others. Examples of wireless networks include cellular-based data systems. The following are several such examples: (1) the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), (2) the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems” (the IS-2000 standard), and (4) the high data rate (HDR) system that conforms to the TIA/EIA/IS-856 standard (the IS-856 standard).
One particular type of WCD is a personal location device. A personal location device is used for purposes of providing location information to the user of the device, in the manner of a GPS or for enabling external tracking of the device, for example by use of a wireless network. It is often desired to provide such personal location devices with low power consumption, using techniques such as Low Duty Cycle (LDC) technology—a technology which enables a device to go into a deep-sleep mode (less frequently transmit or receive on the cellular network) in order to conserve battery life. One disadvantage of LDC is that by reducing the active time of a device, tracking and other location monitoring becomes difficult. It is often the case that if an object is to be tracked, there are times during which a very active duty cycle is advantageous.
For the purposes of this invention, “GPS” is intended to describe GPS, as well as other wide area radio geolocation systems, such as GLONASS, Omega, Loran, etc.
Various cellular location services are used to provide geolocation data concerning a cellphone or other wireless communication device (WCD). Most commonly, this is part of an emergency services function, but can also be used for personal tracking and location oriented services such as map directions. The location services may use location services, such as those provided by the wireless communication network, or by a geolocation device such as GPS. “Location” and “location services” are used to describe the determination of a physical location of a WCD. Typically “location” consists of identifying a position of the WCD which can be translated to geographical coordinates.
A geolocation system uses a system of signals to determine geolocation. This is commonly associated with GPS, although ground-based systems are also used. In addition, wireless communication networks often have a capability of providing geolocation based on the communication links. Such location determinations are considered to be reliable terrestrial navigation or geolocation because if the signals are properly received, the determination is reliable to the accuracy of the system. They are reliable in the sense that location is determined based on the operation of a properly based system in which the geonavigation signals are properly received. It is understood that the GPS or other geonavigation system itself may generates errors which are not detected by the wireless communication system; however the geonavigation system is considered to be reliable in the sense of detecting location.
Tracking based on a cellphone or other WCD by use of a geolocation system results in a location only accurate to a few meters at best, and sometimes is only accurate to hundreds of meters. This is a separate issue from the “reliable” nature of the GPS signal. This is often sufficient for location services, but for some items, like keys, a purse or a small pet, it may still be hard to locate the lost object even when directed within a few meters of the object.
Obtaining location data for a WCD beyond that provided by a determination of a localized radio reception area is useful for a number of reasons, such as providing emergency services and providing consumer directional assistance. Emergency services callers dial a police emergency number, whereupon emergency services are dispatched to the caller's location. This is accessed by using an emergency services number or universal emergency telephone number, such as “999” (UK), “911” (North America), “112” (Europe), etc. Many emergency call centers have a feature called “marking of origin”. The phone number of the caller is transmitted via the network, and the address corresponding to the phone number is located in the database of the telephone network provider. By using digital maps and mapping applications, the position of the address can be shown on the map instantly as calls arrive.
In the case of landlines, the location of the caller is usually provided by telephone account data or the like, referred to as automatic number identification (ANI) in North American SS 7 systems. Modifications of ANI, called “Enhanced 911” have been implemented in North America, but these services are still based on a fixed subscriber location.
In the case of mobile telephone services, the physical location is not inherent in the connection service. Cellular telephones are generally not located by ANI information such as area code and prefix. Automatic Location Identification (ALI) is intended to provide physical location of cellular telephones, either by network-based identification of location or by WCD based geolocation.
There are instances in which ALI is unable to accurately determine the location of a WCD, most notably when a GPS-enabled WCD is unable to acquire the GPS satellite signals. By way of example, metallization of a building will create a Faraday enclosure for GPS reception. Thus, while “Enhanced 911” mandates partial and full ALI capabilities, the ALI data may not be available. Location services are limited, in part because of the difficulty of receiving sufficient GPS signals with mobile telephones, particularly from within an enclosure.
The data used to perform location can be obtained from the WCD itself, as is the case of GPS, primarily from the network base station, as is typical with Angle of Arrival (AOA), Time of Arrival (TOA) and Time Difference of Arrival (TDOA), or a combination of network determination and device determination. It is possible to enhance the GPS tracking ability by use of signals from a base station. This implements techniques known as assisted GPS (A-GPS). One A-GPS function provides additional information, including satellite constellation data, to the WCD through a communications datalink, to significantly improve the chance for acquiring GPS signals. A second location technique used in association with wireless networks uses triangulation from the base stations, such as Angle of Arrival (AOA), Time of Arrival (TOA) and Time Difference of Arrival (TDOA).
GPS based systems in particular consume significant battery power from a receiver, so it is advantageous to leave the location function turned off during normal operation. In the case of network-based location services, the location services depend on the extent of the WCD's level of communication with the network. In a quiescent state, the WCD may only provide signals sufficient to allow the network to identify a particular transmitter sector to use to communicate with the WCD. Users of WCDs also turn off location services so as to avoid the potential for commercial abuse of the location data. Many WCDs which are GPS enabled are configurable to limit location services to emergency calls, or to only turn on the location service when location-based communication services are desired, such for obtaining directions. In such cases, the location device is activated by activating an emergency call service, or launching of location-based communication application.
Long distance and local location and tracking can be solved separately. Tracking devices either send data back over a communications network which contains the location, or they emit a beacon signal that can be tracked by another device within an appropriate proximity—typically some type of radio receiver. These devices either operate in one mode, or the other and employ two separate tracking functions.
Tracking based on a cellphone or other WCD by use of a geolocation system results in a location only accurate to a few meters at best, and sometimes is only accurate to hundreds of meters. This is a separate issue from the “reliable” nature of the GPS signal. This is often sufficient for location services, but for some items, like keys, a purse or a small pet, it may still be hard to locate the lost object even when directed within a few meters of the object.
Additionally, indoors as described above, an A-GPS geolocation system can result in locations that vary by hundreds of meters. For example, FIG. 1 is a map depicting locations determined by AGPS for a WCD 103 inside a building, shown as “Building L”, at a location estimated to be at position 111. The WCD location samples are indicated by the small squares (▪), not separately identified. As can be seen, the WCD “wandered” within the building, outside the building, and at times extending toward Building KS at location 125. While it is not clear whether the user was at Building KS, the WCD was left on the desk in the office at location during the whole time 111 and in reality did not follow the user to Building KS 125 or another location. Tracking of the WCD was accomplished by the wireless network; however various factors, mostly related to signal propagation presumably resulted in the variation in detected location. This is indicative of the ambiguity of tracking a WCD inside a building.
FIG. 2 is a map depicting locations determined by AGPS for several WCDs. A significant percentage of the samples are taken inside a building at position 111. Most locations for the building are in the general area of the building, with that area indicated (at 135); however some depict movement (e.g., 243, 244) across the large highway 255, which did not occur. Other indications indicate other local areas (at 125-127). In the case of some adjacent areas such as 266, there's an ambiguity suggesting that the user may have been walking with the device across those areas, but other locations (273, 275, 277) are suggestive of inaccurate results.
These patterns of location have some degree of predictability. The map of FIG. 2 depicts locations determined by AGPS for several WCDs left inside the building at the same location. As can be seen, the patterns represented by the WCDs differ for each WCD. Tracking these WCDs gives the impression that they are wandering, either across the roadways or into neighboring buildings, and in several cases nearly a kilometer away (at 273). It is likely that the WCD would “wander” further (according to the sample location readings), except that the location readings are constrained by the WCD's communication with a sector within the network.
FIGS. 3A and 3B are maps depicting the results of tracking the 5 devices from FIG. 2 while walking outside with the devices. Results near Building L are scattered, although some locations correspond to actual movement of the WCD outside of Building L. Other results are further away, but based on the cultural features of the map, it can be seen that they reflect accurate indications of location. For example, the WCDs were detected along the roadways (at 335-338) or in a retail area (at 341). These readings are representative of readings taken outdoors, which are generally much more accurate than those taken from within a building.
While the maps may be interesting, the ambiguities mean that, for example, location services provided for emergency services are unable to precisely locate the WCD or more significantly a user sending a distress signal. If one is looking for a small object, the information provided by the location service merely indicates that the object is within perhaps half a city block, which is often inadequate for purposes of more precise identification of the location of an object.
Rate instruments have been used to detect location, most notably on aircraft. Rate instruments include inertial reference platforms and similar instruments that measure acceleration, changes in direction, changes in velocity, attitude changes and the like. One example is a set of three-axis gyroscopes and accelerometers used to obtain accurate attitude, direction and position information of a platform in inertial space. Given sufficient data including an original position, it is possible to determine the position of an object based on rate measurements derived from rate instruments, with corrections made for precession and similar errors. For purposes of this invention, “rate” is intended to refer to motion and other positional change, including acceleration, velocity and other changes in velocity.